GM Crop Concerns

A questionable study claims that rats fed approved genetically modified maize developed cancer and died early.

By Beth Marie Mole | September 20, 2012

Researchers at the University of Caen in France claim that a diet of Monsanto’s genetically modified (GM) maize—which has been approved for consumption in the United States since 2000—caused rats to suffer organ damage, develop debilitating tumors, and die early. But the 2-year study, which was published yesterday (September 19) in the journal Food and Chemical Toxicology, has drawn swift criticism from scientists who point out missing data and questionable methods.

In the study, researchers divided rats into 4 groups: one fed GM maize—resistant to Monsanto’s week-killer, Roundup—that had traces of Roundup; a second fed GM maize without Roundup; a third fed conventional maize and Roundup-laced water; and a control group given conventional maize and pure water.

Within 2 years—a rat’s normal lifespan—the study reports that of the rats fed GM maize, 50 percent of males and 70 percent of females died early, compared to 20 percent of males and 30 percent of females in the control group. Further, researchers noted liver and kidney damage and large mammary tumors in the rats fed GM maize.

But other scientists found flaws in the study. “This strain of rat is very prone to mammary tumors particularly when food intake is not restricted," Tom Sanders, head of nutritional science research at King's College London, told Rueters. He noted that the study did not disclose the rats’ food intake or growth rate.

He added that he was also suspicious of the analysis. “The statistical methods are unconventional,” he said. “It would appear the authors have gone on a statistical fishing trip.”

Mark Tester, a plant geneticist at the University of Adelaide, further questioned how scientists could have missed such significant health threats in the past. “If the effects are as big as purported, and if the work really is relevant to humans, why aren't the North Americans dropping like flies?” Tester wrote to Reuters in an email.

But Michael Antoniou, a molecular biologist at King's College involved with the study, stands by the findings. The data is “strong enough to withdraw the marketing approval for this variety of GM maize,” pending further testing, he told Reuters.

Why do you offer that headline? 'A questionable study'; whose idea? And 'swift criticism from' TWO scientists, one of whom is already proven to have a financial interest in foodsciences company. When I read (elsewhere) on it, I see, ["The French study, however, found a series of adverse health effects in rats fed with the corn.

In this study, conducted on 100 female and 100 male rats, the animals were given either Roundup-resistant corn, the Roundup herbicide or both. Animals in all three of these test groups experienced adverse health effects and died earlier than rats in the control group, who were given regular corn and plain water.

"The results were really alarming," said Professor Gilles-Eric Seralini, co-director of the Risk Quality and Sustainable Environment Unit at the University of Caen, France and the study's lead researcher. Mammary tumors began to appear in females after 4 months, he said, and "after one year there was a high increase of a number of (kinds of) tumors. Almost every female rat had two or three tumors," said Seralini in a Wednesday press conference.

Up to 50 percent of males and 70 percent of females fed with GM corn died before their deaths could be attributed to normal aging, compared with 30 percent of males and 20 of females in the control group who died prematurely.

Tumors grew more frequently and rapidly among most test groups than among the control group. After 23 months, 50 to 80 percent of the treated female rats (percent depending on group) had developed tumors, while 30 percent of female control rats had tumors. The group treated with Roundup showed the greatest incidence of tumors. Of the females in this group, 80 percent developed at least one and up to three tumors.

Treated males developed tumors largely in their kidneys and skin, and were two times more likely to have a tumor during the 23rd month than control males. Treated males also suffered liver damage at greater rates.

Test rats were given varying doses of Roundup in their water and NK603 corn in their feed. The lowest doses administered in the study were lower than levels allowed in both the EU and U.S., according to the study.

The lowest treatment level of Roundup alone was at the "usual contaminating level of tap water," explained Seralini.

Test animals experienced severe adverse health effects even at these lowest levels.The authors say this result suggests that both products cause a hormonal imbalance.

"Our data show that, as is often the case for hormonal diseases, most observed effects in this study were not proportional to the dose of the treatment."

"This implies that both the NK603 maize and R(oundup) may cause hormonal disturbances in the same biochemical and physiological pathway," concludes the study.

The fact that groups treated with GM corn alone reacted similarly to those treated with the only the herbicide was surprising, says Seralini.

"We were really interested by the results of the GMO alone that was not treated with Roundup," said Seralini. "The groups with the GMO surprisingly also had hormonal disruptions and there were also mammary tumors."

After a detailed analysis of the chemical composition of the animals' diets, researchers found that two compounds in plants that protect animals against mammary tumors and toxicity of the kidney and liver were reduced to 51 percent with the consumption of the GM corn. They concluded that an enzyme that is over-expressed in 80 percent of GMOs was causing this effect, explains Seralini.

An estimated 70 percent of corn grown in the U.S. is Roundup Ready.

According to Monsanto's safety assessment, NK603 is corn into which DNA is inserted to make the plant resistant to the harmful effects of Roundup. Prior studies have shown that the CP4 EPSPS proteins expressed in Roundup Ready corn do not produce toxicity in mice, nor are they similar to known allergens or toxins, and they are rapidly digested in vitro. "]

Well, I am no expert in statistics. I am in favor of GM products. As a scientist, my major concern is about the safety of GMO carrying resistance genes to pesticides or toxin genes. The mouse strain used in this study is the same used in the monsanto paper (Hammond et al, 2004). If they have used a different strain, critics would argue that the studies are not comparable.The number of rats evaluated are also the same (actually the monsanto paper used 20 rats, but only analyzed data from 10 rats in each group). So, why no one drew criticism about the small sample in the monsanto paper (used as support data for the safety of this GM crop). This strain of rat is prone to endocrine tumors. Do monsanto researchers know about this? If so, why did not they choose a more suitable strain to allow short and long-term studies in the same strain?

Oh, damn, here we go again...Arpad Pasztai revisited! He was roundly discredited, but how long did it take? Let's all just eat organic food, with all its afla- and other toxins, and not try to improve anything....

hasn't this issue been debated for quite a long time? i mean, for real, why can't you scientists decide on which one is right- are GM foods good for human or not?- you can't just test them on rats and say "okay since the rats die, so will we", you have to consider testing them on human too.. seriously guys, stop intimidating us the average consumers with ambiguous scientific results

Whether or not it was the ideal study in every respect (the statistical analysis is rather complicated), the results clearly warrant further non-industry funded trials over the long term. I'm all for genetic improvement, but this is disconcerting.

Why do you offer that headline? 'A questionable study claims'; whose idea was that? And 'swift criticism from' TWO scientists, one of whom is already proven to have a financial interest in foodsciences company. When I read (elsewhere) on it, I see,

AbstractThe health effects of a Roundup-tolerant genetically modified maize (from 11% in the diet), cultivated with or without Roundup, and Roundup alone (from 0.1 ppb in water), were studied 2 years in rats. In females, all treated groups died 2â€“3 times more than controls, and more rapidly. This difference was visible in 3 male groups fed GMOs. All results were hormone and sex dependent, and the pathological profiles were comparable. Females developed large mammary tumors almost always more often than and before controls, the pituitary was the second most disabled organ; the sex hormonal balance was modified by GMO and Roundup treatments. In treated males, liver congestions and necrosis were 2.5â€“5.5 times higher. This pathology was confirmed by optic and transmission electron microscopy. Marked and severe kidney nephropathies were also generally 1.3â€“2.3 greater. Males presented 4 times more large palpable tumors than controls which occurred up to 600 days earlier. Biochemistry data confirmed very significant kidney chronic deficiencies; for all treatments and both sexes, 76% of the altered parameters were kidney related. These results can be explained by the non linear endocrine-disrupting effects of Roundup, but also by the overexpression of the transgene in the GMO and its metabolic consequences.

Highlightsâ–º A Roundup-tolerant maize and Roundup provoked chronic hormone and sex dependent pathologies. â–º Female mortality was 2â€“3 times increased mostly due to large mammary tumors and disabled pituitary. â–º Males had liver congestions, necrosis, severe kidney nephropathies and large palpable tumors. â–º This may be due to an endocrine disruption linked to Roundup and a new metabolism due to the transgene. â–º GMOs and formulated pesticides must be evaluated by long term studies to measure toxic effects."]

In this study, conducted on 100 female and 100 male rats, the animals were given either Roundup-resistant corn, the Roundup herbicide or both. Animals in all three of these test groups experienced adverse health effects and died earlier than rats in the control group, who were given regular corn and plain water.

"The results were really alarming," said Professor Gilles-Eric Seralini, co-director of the Risk Quality and Sustainable Environment Unit at the University of Caen, France and the study's lead researcher. Mammary tumors began to appear in females after 4 months, he said, and "after one year there was a high increase of a number of (kinds of) tumors. Almost every female rat had two or three tumors," said Seralini in a Wednesday press conference.

Up to 50 percent of males and 70 percent of females fed with GM corn died before their deaths could be attributed to normal aging, compared with 30 percent of males and 20 of females in the control group who died prematurely.

Tumors grew more frequently and rapidly among most test groups than among the control group.

Having looked at the paper, I donâ€™t see any statistical analysis. It seems the mortality effects come mainly from the very early deaths of 2 to 5 males, depending on what is early. Since there are 9 treatment groups and only one control per sex it is not surprising that the first two deaths were in treatment groups, nor particularly surprising that the next 3 deaths were not in the controls. (Note the â€˜0â€™ histogram in each graph, and the dotted line, are the same on each graph.) There was only a 50% chance that one of the first 5 deaths would be in the control group, and as we can't have half a rat, zero is as good a fit as 1. Looking at long term survival, AFTER 600 days the male rats fed on GMO maize are consistently surviving better than the controls. I see no case for GM to answer on mortality or longevity. Considering the females and their tumours, it again appears that one or two females per treatment group are being euthanized because of tumours before the controls. The data suggest that either maize or chronic glyphosate poisoning contribute to disease, although there is again only the one batch of control females for the 9 treated batches, so there is a 9 to 1 likely hood that the worst affected group will be one of the treatments, not the controls. The fact that there is no dose dependence reported suggests that this is random data. An obvious control would be rats fed on various rates of non GM maize added to their diet, but this was not done. Being cynical, I also think the control females were a remarkably healthy lot, although 6 of the 10 developed pituitary pathologies. The difference between tumours in males and females suggests peculiarities of the rat strain used, and the high incidence of disease in the controls does question the suitability of this strain for this experiment because of the high background disease noise. The experiment was not performed blind, as far as I can see, and if the experimenters knew which group were the controls then human nature would have downplayed their pathologies. I also wonder how often similar experiments have produced no meaningful result and not been published. In this case the experiment was lucky enough that the controls were marginally healthier for the first year, and developed slightly fewer tumours. All in all I donâ€™t see any reliable overall patterns in this data